I don’t start a new row of entries until I observe the Electron LED breathing cyan.
At such each time, I fill the corresponding cells with y/n to indicate pass/fail on each of the test criteria.
So far, I have not had a single row indicating pass on all 4 tests.
Often, when a test fails, I notice that the electron LED has started flashing cyan - sometimes fast, sometimes slow.

I inserted some calls to Cellular.RSSI() into my test code.
It consistently returns signal strength of around -100dB (range -95 to -111) and quality of 7. Both of these are distinctly marginal in my estimation. I hope the outdoor antenna and extension cable that I have ordered will help.

In the meantime, testing continues.

I implemented the improvements you suggested in my test code. Thank you for the input.